"Dinos A to Z: Mosasaur" introduces the mosasaur, a giant marine reptile that lived about 65 to 75 million years ago during the age of dinosaurs. The video explains that mosasaurs were not dinosaurs, but aquatic reptiles adapted to ancient oceans such as the Great Western Interior Seaway. Key science concepts include fossils, paleontology, predators, adaptation, vertebrae, scales, flippers, and prehistoric life. It also describes mosasaur size, diet, body structure, habitat, and fossil discoveries in places like Kansas and South Dakota. This educational science video supports curriculum topics in Earth science and life science by showing how fossil evidence helps explain ancient ecosystems and changes in Earth’s history.